An Ofcom assessment has predicted that DSL over normal copper phone lines could take virtually the whole country to broadband speeds of 50Mbps or more, as long as optical fibre is laid to the street cabinets used by the phone network.

According to the study, carried out by consultants Sagentia for Ofcom, around 18 percent of the population — those who live within 2km of a phone exchange — could get 50Mbps or faster from new modems installed in phone exchanges. To extend that coverage to nearly 100 percent of the population would require DSL modems in street cabinets.

BT has already begun a 21st-century upgrade to its network, which concentrates on the backbone connecting its exchanges, but it has been assumed that super-fast broadband will require fibre to every home. Industry pressure group the Communications Management Association (CMA) has called for a £15bn government-led initiative to run fibre to all the nation's homes, and BT has begun a £1.5bn programme to take fibre to 10 million homes.

The Ofcom findings suggest that a lower-cost programme to extend fibre out to the street cabinets could give everyone a much faster broadband experience. "Now it just needs someone to install fibre to the street [cabinets]," said broadband commentator Steve Kennedy in a blog post.

The report does not specify the technology required, only stating that it is theoretically possible to go faster than VDSL (very high-speed DSL).

An Ofcom spokesperson warned that the actual broadband speeds available to the population may be significantly lower than 50Mbps, saying that the study was a theoretical analysis of the properties of copper cable, including issues such as cross-talk and resistance, rather than a detailed assessment of the properties of the UK's actual infrastructure.

There may be other problems with faster broadband technology, adding to its cost, the report points out. For instance, such technology may necessitate better wiring in houses to handle the higher frequencies involved, requiring the work of engineers. Also, upgrading an exchange would be complicated if the DSLAM DSL equipment had to be moved out to street cabinets, requiring a big upfront investment for each exchange.

Also, Ofcom may have to weigh in on how any upgrade is handled, to make sure BT takes the option that is best for the country as a whole. When laying fibre from an exchange to a cabinet, BT may prefer to cable up the nearest cabinets — referred to as the 'best is first' scenario — as this would be cheapest, the report states. The more expensive 'worst is first' option, cabling up the cabinets furthest away, would aid the closing of the digital divide more, by helping those whose broadband speeds are currently worst — and might need to be backed by Ofcom rules, the report suggests.

Reaction to the report has been strongly positive on discussion boards. "Finally Ofcom spouted out something useful, but what many of us have known for ages," said one commentator on Thinkbroadband.com. "Roll on the investment and rollout please BT."